Hydrodynamic brake



Nov. 4, 1947. L. R BUCKENDALE HYDRODYNAMIC BRAKE Filed Jfily 31, 1944 4 Sheets-Sheet l HMHH Nov. 4, 1947. 1.. R. BUCKENDALE HYDRODYNAMIC. BRAKE 4 Filed July 31, 1944 4 Sheets$heet 2 I m w T a k\ I .J- INVENTOR AA WAL-NCE A. Baa/(5mm) 5,

ATTOR/YE Y6 NOV. 4, 1947. BUCKENDALE 2,429,989

HYDRODYNAMIC BRAKE ,u I y H v MW W A TTOR/VE Y5 1947- I I L. R. BUCKENDALE 2,429,989

HYDRODYNAMIC BRAKE Filed July 31, 1944 4 Sheets-Sheet 4 ATTOR/VE'YG Patented Nov. 4, 1947 HYDRODYNAMIC BRAKE Lawrence R. Buckendale, Detroit, Mich., assignor to The Timken-Detroit Axle Company, Detroit, Mich., a corporation of Ohio Application July 31, 1944, Serial No. 547,337

This invention relates to hydrodynamic brakes and more particularly to a braking mechanism of this type which may be advantageously employed to apply brakin'g torque to the power transmission shaft of a motor vehicle and for other purposes. The practical operation of such brakes, as heretofore proposed, has been found more or less unreliable and uncertain to progressively apply the braking torque to the rotating member in increments or stages of definite value. These prior suggestions involve the provision of compl-icated and costly adjusting mechanisms for regulating the retardent influence of the liquid upon a rotor fixed to the rotating member or shaft, or the use of a selectively shiftable gear mechanism to vary the relative speeds of rotation of the rotor and its housing or casing. Also, inadequate provision was made for the cooling of the braking liquid, maintenance. costs were excessive, and the design and construction of such devices failed to meet the space limitations .required for their use in motor vehicles.

It is, therefore, the general object and purpose of my present invention to provide a hydrodynamic brake constructed with a view to obviating the deficiencies of prior art brakes of this class, and particularly designed for application to motor vehicle drives, though not limited to such use.

Another object of the invention is to provide a multi-stage hydrodynamic brake having a single unit casing or housing structure fixed to the member to be braked, and a plurality of independently rotatable rotors cooperatively associated with said casing through a liquid medium to normally rotate as a unit with the casing, and means individual to each rotor to arrest the rotation thereof and apply braking torque to said casing and member. A further object resides in the provision of a novel casing unit structure and multiple rotors of difierent diameters, the respective rotors and the casing having confronting liquid receiving 15 Claims. (Cl. 188-90) circulation of cooling air over the surfaces of the rotor casing.

A still further object of the invention is to provide the casing structure with a liquid circulating system for the purpose of internally cooling the casing walls and efl'ectively lubricating all moving parts. The invention has for another of its objects, in one embodiment thereof, to provide mechanical braking means for controlling or stopping rotation of the rotor independently of the power transmitting shaft and outer casing structure, and additional means operatively associated with the rotor for positively reversing its direction of rotation with respect to said shaft and easing structure so that the relative velocity factor will be increased for the transmission of high braking torque value to said shaft.

It is also an important object of the invention to provide novel means formaintaining an adequate supply of liquid to the rotor casing regardless of temperature changes, and to bleed air and vapor therefrom.

Among other subordinate features of the invention, reference is made to the. simple and rugged structural form and compact assembly of the several parts, for eflicient functional operation in a minimum space, thereby enabling the device to be readily adapted to motor vehicle use at comparatively low initial cost and maintenance expense. 1

Other objects and advantages of the present invention, not above specifically referred to, will be made manifest in the following description and subjoined claims, when considered in connection with the accompanying drawings, in which similar reference characters designate corresponding parts throughout the several views, and wherein Figure l is a diametrical sectional view showing one preferred embodiment of my improved hydrodynamic brake;

Figure 2 is a transverse sectional view taken substantially on the line 22 of Figure 1;

Figure 3 is a horizontal sectional view taken substantially on the line 3-3 of Figure 1;

Figure 4 is a transverse section taken substantially on the line 4-4 of Figure l; v

Figure 5 isa detail sectional view taken substantially on the lines 5-5 of Figure 1;

Figure 6 is a diametrical section, similar to vehicle chassis in conventional manner.

In the embodiments of the invention which I have selected for illustration, there is provided a sectional casing or housing structure, which, as shown in Figure 1, may comprise a central section, generally indicated at II, and the side sections I2 and I3, respectively. Each of these casing sections is of general circular form and the central section II includes an outer large diameter portion I4 and a laterally extending cylindrical portion II of relatively small diameter. The parts I4 and I5 are formed with bolting flanges I6 and II, respectively, which. are rigidly secured tosimilar flanges I8 and I9 on the casing sections I2 and I3,

respectively, by bolts and 2I.

The central casing section II has an inner hub portion 22 securely fixed to the periphery of the shaft III, as by the splines 23, and annular members 24 secured by bolts 25 to said hub and abutting the opposite ends of the splines 23. g

A small diameter rotor is associated with the casing section I 3 and the cylindrical part I5 of casing section II, said rotor having an annular head 26 connected by a narrow web 21 with one end of the hub sleeve 28 which extends axially beyond the casing section I3 and loosely surrounds the shaft |0. It will be noted that the radial dimension of the rotor head 26 is appreciably greater than that of the web 21.

The casing section I3 and the part I5 of casing section II are recessed as at 29 and 38, respectively, to receive the inner and outer cylindrical portions of the rotor head 26 for free rotation relative to the casing sections.

A similar rotor of relatively large diameter is associated with the casing sections II and I2, the annular head 3| thereof having a radial dimension which is considerably less than that of the rotor head 26, and of the web 32 which connects said head 3I to the inner end of hub sleeve 33, loosely surrounding shaft I 8 and extending axially beyond the casing section I2. The casing sections are recessed as at 34 and 35, respectively, for free rotation of the rotor head 3| therebetween.

The casing section I3 has a hub portion 36 between which and the rotor hub sleeve 28 a suitable type or anti-friction bearing 31 is interposed and retained in applied position by the annular key 38. A friction brake drum 39 has a hub flange 40 splined to the rotor sleeve 28, as at 4|. At the outer side or the bearing 31 a conventional oil seal 42 is positioned between the hub wall on casing section I3 and the brake drum flange 48.

Casing section I2 also has a hub portion 43 and the anti-friction bearing 44 between said hub and the rotor hub sleeve 33 is retained in place by the annular key 45. A second friction brake drum 46 has its hub flange 41 splined to the rotor sleeve 33, as at 48. At the outer side of bearing 44 the end of the brake drum hub is grooved to receive liquid seal rings 49 and the outer end of the casing hub 42 is recessed to receive the oil seal 56.

The inner hub ends of brake drums 39 and 46 abut the inner race rings of bearings 31 and 44,

, lar liquid receiving chamber 58 and the casing respectively, and are held against outward axial movement on the respective rotor sleeves by the retaining rings BI and 62, respectively ated in annular grooves in the splined ends ofthe respective rotor sleeves. Preferably the ring 52 is bolted. as at. 53, to the hub of brake drum 48.

Preferably, the radial wall of each brake drum 39 and 46 is provided with a series of circumferentially spaced openings 54 and adjacent to each opening a reinforcing web 65 connects said wall with the cylindrical drum wall extending inwardly towards the rotor casing. These webs also act as fan blades to direct air currents outwardly between the edges of the brake drums and the casing walls to cool the latter. Conventional friction brake bands 55 and 51, respectively, are associated with the drums 39 and 46 and are adapted to be independently applied to the braking surfaces of said drums by any well known manually operable means.

The casing section I I is provided with an annusection I2 with an annular chamber 59,- said chambers being connected at diametrically opposite points by passages 6| and 62 in the walls of the respective casing sections, corresponding passages being connected in mating relation at the bolting flanges I6 and I8. The wall of the cylindrical portion I5 oi. casing section I I also has passages 63 communicating at one of their ends with passages 6| and mating at their other ends with passages 64 in casing section I3, which communicate with the annular chamber 65 in the latter casing section. The several interconnected casing chambers 58, 59 and 65 are supplied with liquid through a plurality of inlet openings 66 in the wall of the chamber 65.

The rotor heads 26 and 3|, and adjacent parts of the casing structure, are of similar cellular construction, and in the drawings the same ref erence characters have been applied t corresponding parts thereof. Referring now to Figures 1 and 3, each rotor head has two annular series of cells 61, separated by the radial wall 68, the open side of each of said series of cells being in adjacent confronting relation to the open side of a similar series of cells 69 in one of the casing sections. The rotor cells 61 are defined by the circumferentially spaced webs I0 and the casing cells are similarly defined by the spaced webs 1|. Preferably the rotor cell forming webs 10 are at a slight angle to the axis of the rotor, as seen in Figure 3,

With each of the cell formin webs 'II of the casing a liquid jet delivery nozzle 12 is integrally formed, the discharge end of the nozzle bore 13 opening upon the edge of said web at the approximate radial center of the adjacent rotor cells, and at an oblique delivery angle with respect to the axis of rotation of the rotor.

The two sets of nozzles 12, associated with the rotor head 26, deliver low velocity liquid jets into the cells 61 at opposite sides of said head from the casing chambers 58 and 65, respectively. Preferably, in order that the jet velocities shall be substantially equal, the side walls of the annular casing chamber 58, outwardly of the inlet ends of the nozzles I2, are connected by the web 14, having spaced openings I5 therein, through which the liquid may flow into the outer high pressure section 16 of said chamber.

The two sets of nozzles I2 associated with the rotor head 3| deliver high velocity liquid jets into the rotor cells at opposite sides of said head from '59, respectively.

the section I6 of chamber 38 and from, chamber Preferably, the liquid medium, with which the chambers of the casing structure are filled, is a suitable grade of oil, which also lubricates all relatively moving parts of the mechanism. To this end the ducts ll, formed through the inner side of the rotor heads 26 and 3| at circumferentially spaced intervals, discharge oil from the rotor cells on opposite sides of the rotorwebs 21 and 32, to flow to the bearing 44 and between the rotor hub sleeves 33 and 28 and shaft l0, and between the latter sleeve and the inner cylindrical wall of easing section l3. Sealing rings I8 on sleeve 28 contact the inner surface of said casing wall, and similar sealing rings 19 on the shaft ||l contact the inner surfaces of the rotor sleeves 28 and 33. A conventional type of oil seal is positioned between the outer end of rotor sleeve 33 and the periphery of shaft I0. Also, the liquid is supplied to the outer peripheral surfaces of the rotors through spaced ports 8| and 82 communicating with the passages 62 and 63, respectively.

The hub portion of the brake drum 39 is also formed with an outwardly projecting annular flange 83 in concentrically spaced relation from the rotor hub sleeve 28. A coupling ring 84 extending between said sleeve and flange has a radially disposed arm or lug 85 securely bolted, as at 86, to a fixed part 81 of the supportin frame structure for the shaft I0. Sealing rings 88 and 89 establish fluid tight seals between the fixed coupling ring and the rotatable sleeve and flange 83, respectively. The inner end of the coupling ring 84 is cut away or recessed to form an annular liquid and air receiving space 90 between said ring and the hub of the brake drum 39. The ring 84 is provided with inlet ports, one of which is shown at 9|, with which the threaded end of the elbow nipple 92 is connected. A similar nipple is connected to the other of said ports. The lower ends of liquid feed and air bleed pipes 93 and 94, respectively, are connected to said nipples. The upper end of pipe 93 is connected to the bottom of a tank or reservoir 95 in which a suitable head of liquid is maintained. The pipe 94 extends into said tank and above the liquid level. The top wall of the tank or reservoir is provided with a suitable air vent, indi cated at 96.

Several of the splines 4|, connecting brake drum 39 for unitary rotation with rotor sleeve 28, are milled out to provide longitudinally extending grooves or channels 91 forming communicating passages between the liquid receiving space 90 and the space 98 at the inner side of the hearing 31. From this space the liquid flows through inlet openings 66 into the casing chamber 65. The other casing chambers and the casing and rotor cells are also filled with the liquid through the inter-communicating passages 6|, 62, 63 and 64, Air and vapor are also bled from the casing chambers through the channels or passages 91" to the pipe94.

If desired, in addition to the air circulating webs 55 on the friction brake drums, external heat radiating fins 99 may be formed on the walls of the several casing sections I, 2 and I3.

'From the above description, the construction and operation of this embodiment of the invention will be readily understood. Assuming that the rotor casing has been substantially filled with liquid, when shaft H1 is rotated from a state of rest, the casing structure rotates as a unit therethus independently rotating said rotors.

with. In response to the influence of centrifugal force liquid will be delivered from the casing chambers 58 and 65 through nozzles I2 against the vanes or cell forming webs 10 of the rotor head 28 at low velocity, and against the vanes of the rotor head 3| at relatively high velocity, When the liquid pressures in the cells of each rotor and the cooperating casing cells substantially equalize, the rotation of the casing is transmitted through the liquid to the rotors and the latter will then rotate wih shaft ID at substantially a 1-1 ratio.

When it is desired to brake the shaft III, the

operator first actuates the friction brake 56 to retard the rotation of rotor 26 and, in the relative rotation of the casing, the liquid will react at low pressure against the casing cell walls and, through the casing, apply braking torque of low value to the shaft. When friction brake 56 is fully applied, rotor 26 will then be fixed relative to shaft I0 and a definitely predetermined value of braking torque is applied to said shaft. The other rotor 3| now rotates independently of the casing and at a relatively higher speed. due to the high velocity pressure of the liquid jets from the nozzles 12 upon the walls of the rotor cells.

When it is desired to apply a braking'torque of higher value to the shaft I, after releasing brake 56, the operator actuates friction brake 51 to retard rotation of the rotor 3|. It will be noted that the cells of this large diameter rotor and the mating cells of the casing are of much smaller volumetric capacity than the cells associated with the small diameter rotor 26, and being further spaced from the shaft axis the influence of centrifugal force on the liquid is much greater. Therefore, when rotor 3| is retarded, the reaction pressure of the liquid on the walls of the associated casing cells 69 is considerably greater than that which occurs in the larger cells associated with rotor 26 when rotation of the latter is retarded or stopped. Accordingly, a braking torque of relatively higher value will be transmitted through the casing to shaft I0 and when brake 51 is fully applied to hold rotor 3| in fixed position, a braking torque of another definite predetermined value is obtained.

Of course, the head of liquid in reservoir 95 is sufficiently great to maintain the system substantially filled with liquid at all times. Therefore, when it is desired to apply maximum braking torque to the shaft II] in excess of the energy output of the power source, to prevent rotation of said shaft, as in parking a vehicle, the two friction brakes 56 and 51 are simultaneously fully applied to hold both rotors in fixed positions relative to the casing and shaft. The kinetic energy'of the incompressibleliquid bodies in the rotor and casing cells will, during movement of the liquid, effectively retard rotation of the casing and consequently of the shaft l0 and while said brakes are applied the rotors and liquid restrain the shaft and casing against rotation.

Thus it will be seenthat by means of a very simply constructed mechanism, braking torque of a plurality of predetermined values may be impressed upon the shaft l0 and by properly controlling application of the friction brakes56 and 51 intermediate torque values may be obtained to further control the rotating speed of said shaft. It is obvious, of course, that additional rotor units may be provided in those adaptations of the invention where a greater number of definite braking torque values would 'be desirable.

In Figure 601. the drawings I have disclosed an alternative'embodiment of the invention in which 3 the two units are of equal capacity andhave the same maximum braking effect upon the shaft I0. Otherwise, this construction difl'e'rs from-that first described principally in the form and construction ofthe central casing section. --This central section I of the casing is'splined to the shaft The rotor and easing; construction and the means I her 140 within the out r casing in. which is fixed I l to the power'driven' shaft ,I42to rotate therewith.

forsupplyingthe. hydraulic medium to the casing chambers may besin'iilar toithat heretofore described. The-hub lot-the rotor is extended along the shaft in onedirection externally of the casing and has" brake drum I44 ,flxed thereto,

I0 as previously described and has an'inner hollow portion providing an annular liquidreceivingchamber IOI. at the same radialdistance from the. shaft axis the casing is formed with the two annular series of oppositely facing cellsv I02 and I03,' respective- I ly, and a peripheral flange I04 is securedbetween the flanges I01 on the side casing sections I05 outwardly of said-chamberfand and I03 by the bolts I08. The latter casing sec nozzles III and 2, respectively, in similar man ner to the construction shown in Figure 1.- Also similar liquid receiving chambers H3 and H4 tions are formed with the cells I00 and H0 and provided withthe i'rictionpbrake band I45, asin the construction previouslydescribed.

. With the 'rotor' hubya. ciiflerei'itial unit, to control the'relative velocity of the rotor I40 and casing' I4I isv operatively associated. As herein shown: this diflerentialmay be of conventional form having one sidegear I46 fixed to the end'oi th rotor-hubx I43 andthe others'ide gear I41 fixed tothe'gshaft I42. The diflerential pinions I48 are carried by the case I43 which encloses the .;side gears and is loosely supported upon the shaft and circulating passages H5 and H6 are pro- I I5, and'the separating web I23 between the oas-.

ing cells 102 and I03, liquid supply nozzles for I 42. With the outer peripheral wall of the differentialcase a'friction brake band I50 is asso-' ciated.

It will be' evident from the above that when the'brake band; I50 is engaged'with the differential case the rotor I40 is caused to rotate in an opposite direction with respect to the outer cas-f ing I H, thereby-increasing the relative velocity factor and applying maximum braking .torque to the power transmitting shaft I42. For the transthe chamber IOI extend inwardly from the outer wall of said chamber as shown at I24. The bores of said nozzles are connected by passages I in the web I23 with outlet ports from the liquid circulating passages H5 and H5, as indicated at I26. Thus when the system is eventually filled with liquid from the tank or I'GSGIVOIL'BIS previously explained, the liquid will flow through ports I26 and nozzles I24 until the centralcasing chamber ml is substantially filled.

The nozzles I21 and I28, alternately disposed mission-of lower braking torque values to the shaft I42 the brake band I45 is engaged with drum I44 to control or stop rotation of the rotor member I40.' Byfsuitabl'e connections with the opera- ,tors control lever brake I45 may first be applied to stop rotation oft'he rotor I40,-and upon further movement of said lever .the brake I45 is re- I leased and brake I50 applied to the differential case to reverse rotation of the IOtOr member I40.

If the fluid volume is'maintained at all times on the vrotor-and casing blades, in the manner above explained, thecharacteristics of the hydrodynamic brake will always be predetermined.

on opposite sides of the web I24, deliver liquid jets, centrifugally discharged from chamberv I0],

into the adjacent cells of rotors II1 andI'IB rev spectively. In this modified construction each rotor H1 and I I8, at the inner ends ofthe hub sleeves I I9 and I20, respectively, is formed with an external cylindrical shoulder I29 and I30, respectively. These shoulders are provided with sealing rings I3I and I32 in contact with the respective casing sections I05 and I06, at the inner sides of the bearing I33 and I34. The means for supplying the system with liquid and for bleeding air and vapor therefrom is substantially the same asv above described in connection with the preferred embodiment of the invention.

The operation of this alternative construction is the same in principle as that previously described. However, due to the fact that the two rotors are of the same diameterandthe rotor'and casing cells of like volumetric capacities, when either of the friction brakes I2I or I22 '15 fullyapplied to hold the associated rotor against rotation, the same braking torque value will be transmitted to the shaft I0. When the two fric- ..tion brakes are simultaneously actuated, the I braking torque value is multiplied to stop rotation of the shaft I0 and hydraulically lock the casing structure and rotors against relative required.

This embodiment of the invention may bedesigned as acomplete self contained unit, not particularly dependent on-the characteristics of the vehicle'drive or its gear ratios, since the ratios of the differential gearing may be predetermined as From the-foregoing it-will .be seen that I have provided a hydrodynamic brake embodying a very compact organization of" simply constructed mechanical parts, which is admirably adapted for use on motor vehicles, since it can be operatively mounted ina comparatively small space. As provision is made for the selective transmission of a multiplicity of braking torque values, the rota- .tion of the power driven shaft may be effectively controlled as occasion may demand. The elimination of all gearing,.and the means which I provide for adequately lubricating all moving parts and maintaining the liquidat relatively low temperature, contributes greatly to, a low maintenance expense in the operation of such an'apparatus.

"The invention mayjbeembodied in other specific' forms without departing from the spirit or essential characteristics thereof. The 1 present the drawings I have-shown an embodiments are therefore 'to be I considered in all respects asv illustrative and notrestrictive, the scope of the invention being indicated by thev appended claims rather than by the'fo'regoing description, and all changes which come within the meaning and range of equivalency of theclaims are therefore intended to be embracedtherein.

What is claimed and desired to be secured by United States Letters Patent is:

1. Hydrodynamic braking mechanism comprising a casing structure adapted to be fixed to a rotary member, means within said structure including a member axially fixed relative to said casing structure and rotatable independently thereof under pressure of a hydraulic medium induced by centrifugal force in the rotation of said structure, said independently rotatable member having a hub portion, anti-friction bearing means joumalling said hub portion in one side wall of the casing structure, means for mechanically braking said member to create a reactive pressure influence of the hydraulic medium on the casing structure and transmit braking torque to said rotary member, said means including a brake drum secured upon said hub portion, and a fluid tight seal at the outer side of said bearing between said casing structure and the brake drum.

'2. The braking mechanism defined in claim 1 in which said first named means includes a plurality of rotors freely rotatable relative to each other, and said braking means comprises mechanical braking devices individual to the respective rotors.

3. The braking mechanism defined in claim 1 in which said first named means includes a plurality of rotors freely rotatable relative to each other having pressure impulse receiving heads of relatively different diameters, and said braking means comprises selectively operable braking devices individual to the respective rotors.

4. The braking mechanism defined in claim 1 in which said first named means includes a plurality. of independently rotatable rotors each having a peripheral head provided with an annular series of liquid receiving cells coacting with a confronting series of cells on the casing structure, the cells associated with the respective rotors being of relatively difl'erent volumetric capacities.

5. The braking mechanism defined in claim 1 in which said first named means includes a plurality of independently rotatable rotors of relatively different diameters, each having a peripheral head provided with an annular series of liquid receiving cells coacting with a confronting series of cells on the casing structure, the cells associated with the respective rotors being of relatively diilerent volumetric capacities.

6. In combination with a rotary member, casing structure comprising three chambered sections adapted to receive a hydraulic medium, means for rigidly connecting said casing sections in assembled relation, means for rigidly securing the intermediate casing section to said rotary member, a rotor journalled in each of the other casing sections for independent rotation, the adjacent casing sections having means discharging the hydraulic medium under centrifugal pressure from the casing chambers to pressure impulse receiving means of the respective rotors, and means for independently retarding rotation of said rotors to produce a reactive pressure influence of the hydraulic medium on the casing structure and apply braking torque to said rotary member.

7. The combination defined in claim 6 in which the rotors are of relatively different diameters and the casing chambers associated with the respective rotors are located at different radial disadapted to receive a hydraulic medium, a rotor between each twoadiacent casing sections hav-- ing an annular head of cellular construction, means for rigidly securing the casing sections to a rotary member, said casing sections having means for delivering the hydraulic medium from the casing chambers into the rotor cells under centriiugally induced pressure influence, each of said rotors having a hub sleeve journalled in one of the casing sections, a mechanical braking device for each rotor comprising a brakedrum fixed to the rotor hub sleeve, means for supplying hydraulic medium to the casing chambers, including a fixed coupling ring, and means establishing a fluid tight relation between said coupling ring, one of the rotor hub sleeves, and a part on the brake drum associated therewith.

9. In a multi-stage hydrodynamic braking mechanism, casing structure adapted to be connected to a rotary member for unitary rotation therewith, a plurality of hydraulically impelled rotors associated with said casing structure for rotation with respect to said casing structure and to each other, said casing structure and rotors having means difierentially determining the impelling influence or the hydraulic, medium upon the respective rotors, and means exterior to the casing structure for controlling the independent rotation of said rotors, and operable to selectively retain the same in fixed position relative to the casing structure and rotary member to transmit a braking torque of selected value through the casing structure to said rotary member.

10. The braking mechanism defined in claim 8, in which the rotor hub sleeve is provided with an inlet passage in its periphery communicating with the casing chambers.

11. In combination with a rotary member, a casing fixed to said member, a rotor associated with said casing for tree rotation relative to said casing and member and having a hub extension journalled in a side wall of the casing, said rotor and casing having coasting working cells for a hydraulic medium, ma ually operable means to retard rotation of said otor and transmit braking torque to the rotary member through said casing, including a brake drum fixed to the outer end of the hub extension of the rotor, and means effective to supply the hydraulic medium to said casing during operation including an inlet passage therefor formed in the hub extension of the rotor.

tances from the axis of said rotary member to discharge the hydraulic medium under centrifugal pressures of relatively different magnitudes.

8. Hydrodynamic braking mechanism including a plurality of chambered casing sections 12. In combination with a rotary member, a casing fixed to said member, a rotor having a hub extension Joumalled in the side wall of said casing for tree rotation with respect to said member and casing, said rotor and casing having coacting working cells for a hydraulic medium, and manually operable means to retard rotation of said rotor and transmit braking torque to the rotary member through said casing, including a brake drum fixed to the hub extension of said rotor, said drum being provided with means for circulating air over and in contact with the walls of .said casing.

13. Hydrodynamic braking apparatus comprising an impeller casing adapted for rotation with a supporting drive shaft; a turbine member within said casing, a hub on said turbine member rotatably mounted and axially fixed on said shaft and extending through said casing, a. brake drum on said hub externally 0! said casing, and a fluid tight seal between said hub and said shaft externally of said casing.

14. Hydrodynamic braking apparatus compris- REFERENCES CITED The following references are of record in the file of this patent:

Number Number UNITED STATES PATENTS Name Date Walker Dec. 14, 1926 Anderson et a1 Jan. 2, 1940 Anderson Oct. 22, 1940 Denman Apr. 28, 1942 Dick May 6, 1941 Wemp Mar. 9, 1937 FOREIGN PATENTS Country Date Great Britain May 28, 1937 

